MICROBIOLOGICAL ASSESSMENT OF COMMERCIALLY PREPARED YOGHURTS SOLD IN ABIA STATE, NIGERIA

ABSTRACT

Yogurts are ready to drink foods commonly taken for energy production and for health in Nigeria. Therefore this study was carried out to determine the microbial and microbiological assessment of commercially prepared yogurts sold in Umuhaia to evaluate their food safety. The commercially prepared yogurt products were purchased from vendors and transported for microbial and microbiological analyzed using standard laboratory methods. A total of 26 bacterial strains and 4 fungi were isolated from ten (10) samples of yoghurt for microbiological assessment of yoghurt. The isolate were identified by morphological characteristics, pigmentation on media, microscopy, biochemical and sugar fermentation methods. The details of these isolates and their percentage occurrence comprising Bacillus subtilis (5), Escherichia coli (4), Staphylococci aurues (2), Lactobacillus species (8), Klebsilla species (3),  Aspergillus flavus (1), Mucor alternaria (1) and Saccharomyces cerevisiae (2) The Lactobacillus species bacterial has the highest number of bacteria isolates (26.67%) while the lowest isolates were recorded in aspergillus flavus and Mucor alternarian with (3.33%) respectively. There were significant decline in pH, temperature and titratable acid. This study has shown that most yogurts contain probiotics isolates including Lactobacillus and Saccharomycess which are therefore beneficial for human consumption, therefore all effort should made to sustain the standard of yogurt.

TABLE OF CONTENTS

Title page ﾿ i ﾿

Certification ﾿ ii

Dedication ﾿ iii

Acknowledgements ﾿ iv

Table of Contents ﾿ v

List of Tables ﾿ vii

Abstract ﾿ viii

CHPATER ONE

1.0 ﾿ INTRODUCTION

1.1 ﾿ Objective of the Study ﾿ 3

1.2 ﾿ Statement of Problem ﾿ 3

1.3 ﾿ Significance of the Study ﾿ 3

1.4 ﾿ Limitation of the Studies ﾿ 3

CHAPTER TWO

2.0    ﾿ LITERATURE REVIEW

2.1    ﾿ Yoghurt Potentials ﾿ 4

2.1.1 ﾿ The Biochemistry behind Yogurt ﾿ 4

2.2 ﾿ Yogurt Production ﾿ 7

2.3 ﾿ Benefits of Yogurt ﾿ 8

2.4 ﾿ Probiotics ﾿ 10

2.5 ﾿ Current Problems ﾿ 12

2.6 ﾿ Improving Functionality of Yogurt ﾿ 14

2.6.1 ﾿ Towards a "Superior" Yogurt ﾿ 16

2.6.2 ﾿ Temperature and pH control of yoghurt ﾿ 17

2.6.3 ﾿ Mechanical Rationale for Potential Benefits of Yoghurt on 

﾿ Gut Function and Health ﾿ 18

2.7 ﾿ Laxation ﾿ 19

2.7.1 ﾿ Yoghurt and diseases of the gastrointestinal tract ﾿ 19

2.7.2 ﾿ Diarrheal diseases ﾿ 21

2.7.3 ﾿ Colon cancer ﾿ 22

2.7.4 ﾿ Inflammatory Bowel Disease ﾿ 23

2.7.5 ﾿ Helicobacter pylori ﾿ 24

CHAPTER THREE

3.0    MATERIALS AND METHODS 

3.1   Sample collection ﾿ 26

3.2    Media Preparation ﾿ 26

3.3    Microbiological Analysis ﾿ 26

3.4 ﾿ Identification of Isolates ﾿ 27

3.5 ﾿ Gram Staining Techniques ﾿ 27

3.6 ﾿ Motility Test ﾿ 27

3.7       Biochemical Tests ﾿        27

3.7.1 ﾿ Catalase Test ﾿        27

3.7.2    Coagulase Test (Slide test)                                                                                         28 ﾿

3.7.3    Oxidase Test ﾿        28

3.7.4    Citrate Utilization Test ﾿        29

3.7.5     Indole Test ﾿        29

3.7.7     Voges-Proskauer Test ﾿        29

3.7.8     Methyl Red Test ﾿        30

3.7.9     Sugar utilization test  ﾿        30

3.8 ﾿ Lactophenol Cotton Blue Staining ﾿ 31

3.9 ﾿ Physiochemical Analysis  ﾿ 31

3.10 ﾿ Measurement of pH  ﾿ 31

3.11 ﾿ Determination of Titratable Acidity ﾿ 32

CHAPTER FOUR

4.0 ﾿ RESULTS ﾿

4.1 ﾿ Total microbial counts Cfu/ml of Yoghurt samples ﾿ 33

4. 2 ﾿ Identification and characterization of Bacterial Isolates ﾿ 33 

4.3 ﾿ Identification and characterize of Fungal Isolates ﾿ 33

4.4 ﾿ Percentages occurrence of isolates from yoghurt sample ﾿ 33

4.5 ﾿ Temperature, pH and Titratable acid values of the yoghurt samples ﾿ 34

CHAPTER FIVE

5.0 ﾿ DISCUSSION, CONCLUSION AND RECOMMENDATION

5.1 ﾿ Discussion ﾿ 40

5.2 ﾿ Conclusion ﾿ 42

5.3 ﾿ Recommendation ﾿ 42

﾿ References ﾿ 43